2017-07-08 / News

Unseasonable Weather Sweeps Through Straits

By Jacob A. Ball

Climate in the Straits of Mackinac is often erratic with a wide range of temperatures and intense storms, but rains that engulfed Mackinac Island for extended periods during the final week of June were unusual, according to a National Weather Service climatologist.

The rainstorms followed several days in which temperatures were in the fifties. Precipitation began Wednesday, June 28, and continued unabated from the early afternoon until sunrise the next morning Thursday, June 29. According to the National Weather Service, more than 1.5 inches of rain fell during this period.

Such long-duration storms are atypical for summer in northern Michigan. Meteorologist Matt Gillen of the weather service said storms of this intensity and duration are more common during the transition seasons of spring and fall.

The recent surge of rainstorms in the Great Lakes basin brought considerable flooding and property damage to communities across mid-Michigan. Mr. Gillen said the composition of the terrain on Mackinac Island and in surrounding areas, however, limits the likelihood of wide-scale flooding in the Straits of Mackinac region. Unlike the middle of the state, which has a surface of mostly clay and rock, northern Michigan is comprised primarily of sand. The porous Island topsoil allows water to seep into the ground faster, so even in long-duration storms, less accumulates on the surface.

The unusual June weather patterns in the region this summer were caused mostly by weather systems that formed in the Pacific Northwest and combined with additional moisture swept northward from the Gulf of Mexico. When these forces come together in the middle of the United States, they are collected by the northern jet stream and swept over the Great Lakes toward the Atlantic Ocean. Mr. Gillen said this system was present throughout June, but only produced large-scale storms a few times.

Forecasts for the coming weeks suggest a reduction in the intensity and duration of any rainstorms that might travel across the Straits as temperatures continue to rise. Recent cool air draining from Canada into the Great Lakes led to a dip in temperatures toward the end of the month. Average temperatures, however, have been above average across northern Michigan since Memorial Day.

Although the high temperature did not reach 60 degrees on several recent days, the average temperature for the month was slightly above historic averages. The weather service recorded temperatures 1.5 degrees warmer in Cheboygan than the historic average there.

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